Cost-effective recycling of materials, such as glass, has become an increasingly important issue to many businesses due, for example, to ever increasing legislative mandates at the federal, state and local levels, and the associated cost of complying therewith. In a recycling process, an entity such as a beneficiator can face several significant challenges, particularly with regard to color sorting and recovery of sufficiently clean glass.
A beneficiator is an entity, within an overall glass recycling system, that typically receives glass from one or more material recovery facilities (MRFs), and further sorts, cleans, and/or otherwise prepares the glass so that it can be used as a raw material, for example, in bottle production. A MRF generally serves as a drop off and gross sorting point for recycled materials so that recycled material such as glass can be transported, for example, to a beneficiator for subsequent processing.
A conventional beneficiator generally processes and cleans glass through two separate processing “lines,” or stages (hereinafter lines). The lines do not have to be physically separate, but rather can be different stages or aspects of an integrated process.
The first line is used to mechanically and/or manually sort glass by color (e.g., flint, amber, green), and remove contaminants. Color sorting is necessary because conventional glassmaking techniques require that like-colored glass be recycled together. A conventional beneficiator usually processes one color of glass at a time, particularly when automated optical sorting is performed, generally due to the added cost associated with providing the equipment and/or labor that would enable two or more colors of glass to be simultaneously color sorted. If a conventional beneficiator sorts two or more colors (e.g., flint and amber) of glass, the entire glass stream must proceed through a series of color-specific optical sorters, or proceed through the line multiple times, once for each color of glass.
The second line is used to further clean, screen, and/or crush glass to achieve size uniformity. For example, the second line may be used to remove ceramics and other contaminants from the glass stream. The second line often; however, is inactive, as the line must wait for the first line to finish processing before receiving the glass stream.
Pieces of mixed color (e.g., flint, amber, green) glass smaller than about 10 centimeters in size are referred to as mixed cullet or residue (hereinafter mixed cullet). A conventional beneficiator typically amasses stockpiles of mixed cullet, which is typically used either as a landfill cover material, or is further processed, at an additional cost, so that it can be used, for example, as a paving material such as glasphalt (a highway paving material in which recovered ground glass replaces some of the gravel in asphalt) and/or aggregate (material such as glass, sand or small stones mixed with a binder such as cement to produce mortars and concrete).
The beneficiator must color sort the mixed cullet if it wants to extract a higher value therefrom. Current manual and automated sorting methods are labor intensive and costly. Moreover, color sorting of mixed cullet is generally not economically viable. The beneficiator may also blend mixed cullet into the color sorted glass, but is limited by the amount of cullet that can be blended into the separated glass because separated glass colors must generally ship with, for example, a maximum 5% color contamination. Beneficiators thus have a growing supply of mixed cullet, which surpasses available supplies of color sorted material to which it may be added.
There is a need in the art for more economically viable methods of using mixed cullet and more economically viable systems and methods for beneficiators to recycle and process mixed cullet. The invention is directed to these, as well as other, important ends.